1. Field of the Invention
The present invention relates to a telephone terminal, a telephone communication system, and a telephone terminal configuration program, which can be installed in an information processing device to enable the information processing device to operate as a telephone terminal.
2. Description of the Related Art
Japanese Patent Application Publication (JP) No. 2002-91496 describes a voice transmitting device in which programs for different codecs complying with different standards are stored in the device and the necessary program is downloaded into a digital signal processor in the device. In a device of this type, the available coding systems are limited to the coding systems implemented by the codec programs stored in the device.
JP 2003-513571 describes a more flexible communication system in which a codebook is downloaded from a system file server into mobile communication terminals or stations, which use the codebook for coding and decoding messages. The codebook is downloadable only within the communication system, however, so it is not possible to match the coding system of a communication terminal operating in a different system. Inter-system communication capabilities are limited accordingly.
With the increasing variety of terminals available for telephone communication, these limitations become increasingly serious. For example, personal computers can now be used as telephone terminals by installing software to make them operate as what are called Internet protocol (IP) softphones. Many types of IP softphone software are available, but with the systems described above, when IP softphone users in different systems communicate with each other, their choice of coding methods is confined to a limited selection of coding methods supported in both systems.